BACKGROUND
England's third trimester maternal pertussis vaccination, introduced in October 2012, was extended to the second trimester in 2016. Maternal vaccination provides high protection against infant disease but routine second trimester vaccination has not previously been assessed.
METHODS
National laboratory-confirmed pertussis case-surveillance determined vaccination history, maternal vaccination history and hospitalisation. Pertussis hospital admissions between 2012-2019 were extracted from the Hospital Episode Statistics dataset. Vaccine effectiveness (VE) was calculated for pertussis cases born between October 2012 and September 2018 using the screening method and matching with a nationally representative dataset.
RESULTS
Higher coverage was observed after earlier maternal vaccination with approximately 40% of pregnant women vaccinated ≥13 weeks before delivery. Cases and hospitalisations stabilised at low levels in younger infants but remained elevated in older infants, children and adults. No deaths arose in infants with vaccinated mothers after 2016.Of 1162 laboratory-confirmed pertussis cases in the study, 599 (52%) were aged <93 days: 463 (77%) with unvaccinated mothers and 136 (23%) with vaccinated.Vaccine effectiveness was equivalent in infants with mothers vaccinated at different gestational periods excepting infants with mothers vaccinated between 7-days pre- and 41-days post-delivery. Children whose mothers were unvaccinated but with vaccination in a previous pregnancy had a VE against disease of 44% (19% to 75%). There was no increased disease risk after primary vaccination in children with mothers vaccinated at least 7 days before delivery.
CONCLUSIONS
National policy recommending vaccination from second trimester increased earlier maternal vaccine uptake with sustained high effectiveness and impact against early infant disease.